There appears to be a degree of confusion regarding the presence of prices on the front flap of dustwrappers on Allen & Unwin, Unwin Hyman and HarperCollins hardback books from The History of Middle-earth, especially concerning the point of sale of such books. The bibliography entries in the History of Middle-earth section of the site list the pricing variants that have been seen. What follows is my own understanding of the situation.

Examples

The Book of Lost Tales 1
1983

The Book of Lost Tales 1 & 2
1983 & 1984

The Book of Lost Tales 1 & 2
1983 & 1984

The Lays of Beleriand
1985

The Book of Lost Tales 1
1988

The War of the Ring
1990

The Shaping of Middle-earth
1991

Sauron Defeated
1992

The Peoples of Middle-earth
1996

There are essentially three variants:

Price printed on flap

No price printed on flap

Price added on a label

Price printed on flap
These were intended for the UK market. Some have been seen with the original price cut off ("price-clipped") and a new price added on a label.

When Book Club Associates bought copies from the trade edition, if they had a printed price, they were clipped before they were dispatched.

No price printed on flap
Opinions vary, but in the 1980s these were probably used for the export market. Presumably some of the exported copies will have prices added on labels - in Australian dollars, Canadian dollars, etc - unfortunately sellers rarely mention such details. From c.1988 they were also sold by Book Club Associates, who had previously issued their own editions of volumes 1-5 of the series.

According to HarperCollins:

"Traditionally, copies sent to BCA had the prices removed from the jackets, but as some older stocks had been re-priced over time (some copies were clipped and/or stickered in the warehouse), it is possible that some unpriced copies were printed for stock, not just for the bookclub."

Price added on a label
These labels were added to unpriced dustwrappers by the publisher and sometimes included their name as well as the price. Allen & Unwin went through a phase in the late 70s and early 80s of not printing a price on any of their dustwrappers - the price was added later on a label. According to a former A&U employee:

"The company's overheads were volitile and it was becoming quite difficult to hold prices for more than two months or so, mostly due to paper and printing cost rises. The books were all priced at the printing stage on the dustwrapper so a decision was made not to print the price on the covers. This would be done with a publisher's sticker in the warehouse in such quantities as to allow for adjustment. i.e. yellow A&U price stickers. The trade were anti this - Wholesalers and W.H.Smith insisted on non-removable stickers which had to be put on with a hot-glue gun. At that time you could only buy these stickers from the makers of the guns for which they provided their standard blank colour sticker and would add print on orders of 25,000 or more. The cost of having less than 25,000 printed stickers was prohibitive. We chose pink, dont ask me why as it wasn't my decision. Had barcoding been in vogue at this time none of this would have been neccessary."

"Regarding the stickers. I am not sure about the details of the change in the sticker types as there was a problem organising the warehouse to deal with the stickering. The original yellow stickers were applied before publication. The request for non-removable stickers came into my department later and was handed to the Production Manager to deal with. I wasn't consulted at any stage as it was a trade department matter. I assumed that all was well as we had no further discussions regarding it. I suspect that when the pink stickers ran out the the yellow ones were used making a nonsense of the whole thing. I don't know for sure so the matter of a definite stickering policy cannot be relied on to have been properly applied. I certanly suspect not."

Examples of the yellow and pink stickers are shown above. In theory the yellow ones should indicate that the book was priced before publication, and the pink ones after, but this is by no means certain.

The policy of not issuing dustwrappers with printed prices seems to have been dropped in 1985, around the time The Lays of Beleriand was published.

A&U and Unwin Hyman price labels have been seen on volumes 1, 2, 4 and 7; as well as on price-clipped copies of volume 5. HarperCollins price labels have been seen on price-clipped Unwin Hyman copies of volumes 6 and 8. Three styles of A&U label have been seen on the first impression of The Book of Lost Tales 1 - see the images above. The yellow ones apparently preceded the pink ones, but how the white variety fits in is unclear.

HarperCollins probably issued all twelve volumes in both priced and unpriced formats. Unpriced copies of volumes 1, 2, 3, 4, 5, 7 and 9 have been seen with the prices added on HarperCollins labels. Other volumes may also have been issued with price labels.

Copies from public libraries have been seen in both priced and unpriced dustwrappers.

Which were produced first?
It is my belief that production of copies both with and without printed prices would have been essentially simultaneous, and that (in most cases) there is little point in trying to distinguish between them or assign priority to one or the other. However, some Tolkien collectors and dealers consider the export copies to be the earliest state of a book, assuming that exported copies would be produced first, so that while they were being transported across the world by sea the domestic copies were being printed and bound.

This assumption is probably based on what we have been told about the publication of The Silmarillion in accounts by Rayner Unwin and Wayne Hammond. However what these collectors and dealers may be forgetting is that the simultaneous worldwide publication of The Silmarillion was not a routine event - only the unusually large pre-publication print run size (hundreds of thousands of copies) and the extended production period (more than three months) allowed A&U to engineer the same publication date worldwide. First impression copies produced by the printers Clowes and Sons were sent out over two months before the publication date to ensure that they reached Canada and Australasia by mid-September - the rest of the world usually had to wait until after the British publication date because the books were in a container on a ship halfway across an ocean. In contrast, the print runs for the first editions of the History of Middle-earth series were all well under ten thousand copies and would have been printed and bound in a relatively short period - perhaps as little as a week or so - which would have made simultaneous worldwide publication impractical and any priority of priced/unpriced dustwrappers largely meaningless.